This project analyzes the role of somatosensory neurons in the parietal lobe during performance of skilled manual tasks. We use a prehension task, in which the hand grasps and manipulates objects, as a model system to examine how sensory cues and previous experience are used to plan and implement skilled hand movements. It aims to understand how information about objects is acquired by the hand through the senses of touch, proprioception, and vision. We propose that sensory responses are perceived in the context of task goals. Neural activity in the posterior parietal cortex (PPC) is hypothesized to reflect task planning needed to grasp objects efficiently and to secure them for manipulation. Neural responses in the primary somatosensory (S-I) cortex confirms or rebuts the subject's expectation of object features, and provides feedback needed for error correction. We will record spike trains and local field potentials of neural populations in PPC and S-I during performance of the task using multiple electrode arrays and digital video measurements of hand kinematics. Aim 1 analyzes the role of sensory information provided by the behavioral cue in modulating neural responses to prehension. We examine how the shape and location of an object are represented in PPC when it is grasped with different instructions and expectations. The studies test hypotheses that the behavioral relevance of object features modifies the motor program developed during task planning, and somatosensory information fed back to the cortex from the hand during task performance. Aim 2 addresses the neural control of bilateral hand movements when both hands perform the same movements together. We will quantify the prevalence of bilateral neurons in each hemisphere that respond equivalently to similar actions performed by each hand, or are specialized for bimanual actions, by comparing temporally uncoupled grasping movements performed separately by the left and right hands, with similar bimanual movements that require coordinated and synergistic actions of the two hands. We also examine whether bimanual behaviors are implemented by synchronous bilateral activation of the two hemispheres using simultaneous recordings from the left and right parietal cortex. Aim 3 explores the role of PPC in decision making when cues are ambiguous. We assess the role of handedness preferences, reward probability and short-term memory in choice of the hand used and object grasped in each trial. This research provides basic insights into the dynamic organization of cortical circuits, the role of prediction in normal hand use, and integration of somatosensory information between hemispheres needed for fine motor control of the hand. An understanding of these cortical processes may have clinical importance for rehabilitation following neurological disorders such as stroke or peripheral nerve injury. Principles of sensorimotor integration derived from this research may prove useful for developing better sensory prostheses or robotic manipulators based on biological models of hand function. This project analyzes the role of neurons in the parietal lobe of the cerebral cortex during performance of skilled manual tasks. It aims to understand how information about objects is acquired by the hand through the senses of touch and proprioception, and is used by the brain when objects are grasped and manipulated skillfully. An understanding of these brain mechanisms may have clinical importance for rehabilitation of hand function following neurological disorders such as stroke or peripheral nerve injury, and for development of better sensory prostheses or robotic manipulators based on biological models of hand function.